Receivers for radio frequency signals are known and receivers for GMSK signals are known. Such receivers are used for some equipment that is employed in Global System for Mobile communications (GSM) systems. Generally these receivers require some form of interference cancellation. One technique for interference cancellation that has been used is referred to as a linear equalizer, wherein the effects of the channel are modeled by filters that independently process a real or in phase part and an imaginary or quadrature part of the received signal. Normally a training sequence included with a GSM transmission is used by the receiver to define the two filters.
The linear equalizer is known to operate well for high levels of certain types of interference, e.g., strong or dominant co-channel interferers. The linear equalizer performs poorly for moderate levels of interference and for combinations of interference, where such combinations may include adjacent channel interferers, co-channel interferers, and noise, e.g., additive white Gaussian noise (AWGN). Other techniques either do not perform as well as the linear equalizer for strong co-channel interferers or are impossible to implement given the length of the training sequence.